Older whites (age 65 and older) are generally more likely than older blacks to develop more advanced forms of age-related macular degeneration, according to a new study in Archives of Ophthalmology. Blacks may even have a protective mechanism against the disease, the study suggests.

Susan B. Bressler, M.D., and her colleagues at the Wilmer Eye Institute, a part of the Johns Hopkins University School of Medicine in Baltimore, studied the eyes of 2,520 patients (1,854 whites and 666 blacks) with an average age of 73.5 years.

Fundus photos showed that the white patients were more likely than black patients to have medium or large drusen, advanced AMD and geographic atrophy.

Specifically, drusen of at least 64m were identified in 56% of both black and white individuals within 3,000m of the foveal center, but drusen larger than 125m were more common among white participants (16% white vs. 11% black individuals).

Drusen at least 250m in size, confluent drusen, or a larger area (greater than 10%) occupied by drusen were each more common among white participants.

Also, white individuals were three times more likely to have focal hyperpigmentation than black individuals. Racial differences were most pronounced for features within the central 1,500m macular zone. Neovascular AMD was present in 1.7% of white participants and 1.1% of black participants, and geographic atrophy was more common in whites than blacks (1.8% vs. 0.3%).

AMD is a complex, multifactorial disease, says Diana L. Shechtman, O.D., associate professor of optometry at Nova Southeastern University College of Optometry. Although we do not know the exact pathophysiology, we have identified a number of risk factors, such as sun exposure, genetics, gender, smoking, age, cardiovascular disease, race, iris color, macular pigment density, etc. The fact that AMD has a higher prevalence among white patients is not new.

However, the researchers say these findings suggest that whites are more likely to progress to advanced AMD than black individuals. Also, they believe that black individuals may actually have a protective mechanism against AMD and other eye abnormalities, but say that more research is necessary.

Dr. Shechtman agrees. Further studies are needed to help justify such findings and, moreover, determine the critical protective mechanism, she says. Knowledge of this may someday help prevent the prevalence of the disease.

Bressler SB, Muoz B, Solomon SD, West SK. Salisbury Eye Evaluation (SEE) Study Team. Racial differences in the prevalence of age-related macular degeneration: the Salisbury Eye Evaluation (SEE) Project. Arch Ophthalmol 2008 Feb;126(2): 241-5.